Wilson Brothers make one, and so does Alan Trees under the Gold Grabber name. Cant go wrong with either, both make quality gear. I believe Royal has one in their lineup as well, If they do, another piece of well made gear.
A cheaper route, if handy with DIY projects, is one with the frame and legs out of PVC, trommel tube out of a couple of cut 5 gal buckets and hardware cloth screen. Just google homemade trommels and something bound to pop up.